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K2 distorted audio on certain freq.

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mduke

K2 distorted audio on certain freq.

I have a new acquisition. I traded my Corsair II for a K2. Going
through it and finding small issues that need to be addressed.
Besides just needing a thorough alignment, have noticed that on 40
meters at 7184.00, the audio is extremely distorted but not on any other
part of that band. I have the owners manual, nothing in trouble shooting
about distortion.
Ser. #3631. K2 IOC 1.07. K2 MCU 203. KSB2 1.07

Every 5 minutes I also here a noise like a quick cyclic pulsing for
about 5 seconds and it goes away.

Does anyone know of a regimen of procedures I could start to
troubleshoot and check these issues?

Thank you

Mike
Kj4pom
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jh3sif

Re: K2 distorted audio on certain freq.

If you have strong pulse noise and noise blanker enabled for eliminating the noise, you may hear signals with some level of distortion.
How distorted depends on the noise strength or pulse width of the noise.
You may reduce RF gain of your receiver to improve relative signal to noise ratio and disable the noise blanker.

73 de JH3SIF, Keith

> 2020/05/24 11:38、Mike Duke <[hidden email]>のメール:
>
> I have a new acquisition. I traded my Corsair II for a K2. Going
> through it and finding small issues that need to be addressed.
> Besides just needing a thorough alignment, have noticed that on 40
> meters at 7184.00, the audio is extremely distorted but not on any other
> part of that band. I have the owners manual, nothing in trouble shooting
> about distortion.
> Ser. #3631. K2 IOC 1.07. K2 MCU 203. KSB2 1.07
>
> Every 5 minutes I also here a noise like a quick cyclic pulsing for
> about 5 seconds and it goes away.
>
> Does anyone know of a regimen of procedures I could start to
> troubleshoot and check these issues?
>
> Thank you
>
> Mike
> Kj4pom
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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mduke

Re: K2 distorted audio on certain freq.

Thank you Keith. I had forgotten to say that, this particular K2 has
only one add on board and that would be the side band board. There is no
noise blanker.
Now I did go through each band looking for a aegment of distortion
that may be present on the other bands but being the time of day is
evening, could only check on 80 and 40 meters. Although earlier before
sunset there was still traffic on 20 meters but the whole band was clean.
All of 80 meters was clean as well was 40 (except again on 7.184). It
sounds like a warbly distortion that a Ten-Tec Omni D or Corsair would
demonstrate when the VFO needs to be rebuilt.
Tomorrow I will record an audio clip and post it.

Thank you again.

Mike
Kj4pom

On Sat, May 23, 2020, 23:32 Keith Onishi <[hidden email]> wrote:

> If you have strong pulse noise and noise blanker enabled for eliminating
> the noise, you may hear signals with some level of distortion.
> How distorted depends on the noise strength or pulse width of the noise.
> You may reduce RF gain of your receiver to improve relative signal to
> noise ratio and disable the noise blanker.
>
> 73 de JH3SIF, Keith
>
> > 2020/05/24 11:38、Mike Duke <[hidden email]>のメール:
> >
> > I have a new acquisition. I traded my Corsair II for a K2. Going
> > through it and finding small issues that need to be addressed.
> > Besides just needing a thorough alignment, have noticed that on 40
> > meters at 7184.00, the audio is extremely distorted but not on any other
> > part of that band. I have the owners manual, nothing in trouble shooting
> > about distortion.
> > Ser. #3631. K2 IOC 1.07. K2 MCU 203. KSB2 1.07
> >
> > Every 5 minutes I also here a noise like a quick cyclic pulsing for
> > about 5 seconds and it goes away.
> >
> > Does anyone know of a regimen of procedures I could start to
> > troubleshoot and check these issues?
> >
> > Thank you
> >
> > Mike
> > Kj4pom
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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Vic Rosenthal

Re: K2 distorted audio on certain freq.

In reply to this post by mduke

The "weird at one frequency" is a known issue and there is a fix.
See <https://www.qsl.net/ve3mcf/elecraft_reflect/K2_VFO_Anomaly.txt>
Also
<http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2_28.html>

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/

On 24/05/2020 5:38, Mike Duke wrote:

> I have a new acquisition. I traded my Corsair II for a K2. Going
> through it and finding small issues that need to be addressed.
> Besides just needing a thorough alignment, have noticed that on 40
> meters at 7184.00, the audio is extremely distorted but not on any
> other part of that band. I have the owners manual, nothing in trouble
> shooting about distortion. Ser. #3631. K2 IOC 1.07. K2 MCU 203.
> KSB2 1.07
>
> Every 5 minutes I also here a noise like a quick cyclic pulsing for
> about 5 seconds and it goes away.
>
> Does anyone know of a regimen of procedures I could start to
> troubleshoot and check these issues?
>
> Thank you
>
> Mike Kj4pom
> ______________________________________________________________
> Elecraft mailing list Home:
> http://mailman.qth.net/mailman/listinfo/elecraft Help:
> http://mailman.qth.net/mmfaq.htm Post:
> mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this
> email list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]
>

Don Wilhelm

Re: K2 distorted audio on certain freq.

In reply to this post by mduke

Mike,

This is the Weird At One Frequency (WAOF) problem. It occurs at the
point where the PLL and VFO frequencies cross, and that usually occurs
near 7185kHz.

First step in the cure is to flush cut every lead in the vicinity of
RF Board U4 and the VFO - so that those small leads cannot act as an
antenna.
Then retest.
If the problem still exists, try removing C88 (soldered on the bottom of
U4 between pins 12 and 13). Retest again.

If still present, remove RFC15 - again on the bottom of the board
between U4 pin 16 and the adjacent solder pad just to the right of pin
16 - replace with a very short jumper wire.

Good luck with it - not all K2s suffer this 'malady', but unfortunately
yours does have the problem.

Does your noise problem occur if you disconnect the antenna? That does
sound like some noise being picked up by the antenna. I have never seen
that behavior in a K2 before, and I have repaired over 1000.

73,
Don W3FPR

On 5/23/2020 10:38 PM, Mike Duke wrote:

> I have a new acquisition. I traded my Corsair II for a K2. Going
> through it and finding small issues that need to be addressed.
> Besides just needing a thorough alignment, have noticed that on 40
> meters at 7184.00, the audio is extremely distorted but not on any other
> part of that band. I have the owners manual, nothing in trouble shooting
> about distortion.
> Ser. #3631. K2 IOC 1.07. K2 MCU 203. KSB2 1.07
>
> Every 5 minutes I also here a noise like a quick cyclic pulsing for
> about 5 seconds and it goes away.
>
> Does anyone know of a regimen of procedures I could start to
> troubleshoot and check these issues?
>
> Thank you
>
> Mike
> Kj4pom
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>